1. Field of the Invention
A condenser with a liquid tank according to the invention is set between the compressor and the evaporator of a steam compression type refrigerator forming an automobile air conditioner. After the coolant compressed by the compressor is cooled and condensed, foreign matter such as water content are removed from the coolant. And the refrigerant thus treated is supplied to the evaporator.
2. Description of the Prior Art
A vehicle air conditioner adapted to cool and dehumidify the inside of a motor vehicle includes a steam compression type refrigerator. FIG. 8 is a circuit diagram showing the fundamental arrangement of a steam compression type refrigerator which has been disclosed in Japanese Patent Publication No. Hei. 4-95522. The gas-phase coolant (high temperature and high pressure) discharged from a compressor 1 heat-exchanges with air while passing through a condenser, thus being cooled and condensed; i.e, liquified. The resultant liquid-state coolant is stored in a liquid tank, and then supplied through an expansion valve 4 to an evaporator 5, where it is evaporated. The temperature of the evaporator 5 is decreased because the evaporation latent heat is taken. Hence, when air-conditioning air is caused to flow in the evaporator 5, this air is decreased in temperature, while the steam contained in said air can be removed. The coolant which has been evaporated and gasified is sucked into the compressor 1, where it is compressed. The above-described operations are cyclically carried out.
The liquid tank 3 forming the steam compression type refrigerator of a vehicle air condition is formed as an unit separate from the condenser 2, and it is connected to a pipe which is connected between the condenser 2 and the evaporator 5. In the case where, as was described above, the liquid tank 3 is a unit separate from the condenser 2, the space of installation thereof is increased as much as that for the liquid tank 3. In addition, it is necessary to secure the liquid tank 3 to the vehicle body in such a manner that it is sufficiently durable against vibration independently of the condenser 2. Furthermore, the manufacture, part control, and assembling work of the pipes connected between the condenser 2 and the liquid tank are required, which increases the cost of the vehicle air condition.
In order to overcome the above-described difficulties, and to solve the problem of manufacturing cost, a structure in which the liquid tank 3 and the condenser 2 are provided as one unit, has been proposed by Japanese Patent Publication Nos. Hei. 3-87572, 4-103973, and 4-131667. FIG. 9 shows the structure disclosed by Japanese Patent Publication No. Hei. 4-103973. The condenser 2 has a pair of header pipes 6a and 6b which are horizontally spaced from each other and are extended vertically (in FIG. 9). Between those header pipes 6a and 6b, a plurality of flat heat-transmitting pipes 7, 7, 7, . . . are provided. Those heat-transmitting pipes 7 are vertically spaced from one another, and extended horizontally. Each of the heat-transmitting pipes 7 is inserted into the pair of header pipes 6a and 6b gas-tight and liquid-tight, in such a manner that its inside is communicated with the insides of the header pipes 6a and 6b. Between adjacent flat heat-transmitting pipes 7, a corrugated fin 8 formed by bending a thin metal sheet zig-zag is held, thus forming a core section. Side plates 10 and 11 are provided on the upper and lower sides of the core section 9 thus formed, respectively. Both ends of each of the side plates 10 and 11 are fixedly coupled to the insides of the upper and lower portions of the header pipes 6a and 6b. Those members forming the condenser 2 are made of aluminum alloy.
The condenser 2 thus formed functions as follows: In the aforementioned core section 9, heat-exchange is carried out between the coolant flowing in the flat heat transmitting pipes 7 and the air flowing in the flat heat transmitting pipes 7, so that the coolant is condensed and liquified. That is, the gas-phase coolant supplied through an inlet pipe 12 which is connected to the upper end portion of the first header pipe 6a (on the right side of FIG. 9), while moving between the header pipe 6a and the second header pipe 6b (on the left side of FIG. 9) back and forth, flows in the flat heat-transmitting pipes 7 forming the core section 9, thus being condensed and liquified. The resultant liquid-phase coolant is pooled in the lower end portion of the header pipe 6a, thus being sent through a coolant sending pipe 13 to the liquid tank 3.
On the other hand, the liquid tank 3 is secured to the outside surface of the first header pipe 6a. That is, a cylindrical casing body 14 of aluminum alloy, which forms the liquid tank 3, is fixedly secured to the side surface of the header pipe 6a by blazing or the like. The lower end opening of the casing body 14 is closed with bottom plate 15, and the upper end opening of the casing body 14 is closed with a top plate 16. The aforementioned coolant sending pipe 13 penetrates the bottom plate 15, and is extended along the central axis of the casing body 14, so that a cylindrical space 18 is formed between the outer cylindrical surface of the coolant sending pipe 3 and the inner cylindrical surface of the casing body 14. The upper half of the coolant sending pipe 13 in the casing body 14 has a number of small holes, 17, 17, 17, . . . , to freely discharge the liquid-phase coolant which has been sent into the coolant sending pipe 13 from the header pipe 6a. In the middle portion of the space 18, a filter 19 made of porous material such as felt is set, and a drying agent 20 such as silica gel and calcium chloride is laid on the filter 19, and a porous retaining plate 21 made of a metal net or punching metal plate is laid on the drying agent 20. The filter 19 and the drying agent 20 form a means for removing foreign matter from the coolant. The lower end portion of the casing body 14 is connected to an outlet pipe 22 to freely take the coolant out of the lower end portion of the aforementioned space 18.
In the use of the condenser with the liquid tank (in the operation of the steam compression type refrigerator having the condenser with the liquid tank), the coolant flowing as indicated by the arrows in FIG. 9, after being condensed and liquified in the condenser 2, is sent into the liquid tank 3. In the liquid tank 3, moisture, foreign matter, etc. are removed from the coolant; that is, the purified coolant is supplied through the outlet pipe 22 towards the expansion valve 4 (cf. FIG. 8) located immediately before the evaporator 5. As was described above, the condenser and the liquid tank are formed into one unit; that is, they can be handled as one unit. Hence, they can be readily installed in a limited space in the engine room. In addition, it is unnecessary to set the condenser 2 and the liquid tank 3 separately for anti-vibration. That is, the installation of the condenser 2 and the liquid tank 3 can be achieved with ease, and it is unnecessary to provide a pipe which connects the condenser 2 to the liquid tank 3. This means that the manufacturing cost is decreased as much.
The conventional condenser with the liquid tank which is designed as described above; however, suffers from the following difficulties: In general, in assembling the liquid tank and the condenser, the first header pipe 6a is connected to the liquid tank 3 by brazing. However, the brazing of those members 6a and 3 (especially 3) are rather difficult, because they are each in the form of a cylinder which is large in thermal capacity. That is, the members 6a and 3 are combined with other members forming the condenser 2 (such as the second header pipe 6b, the heat transmitting pipes 7, the fins 8, and side plates 10 and 11) and fixed with a jig (not shown), and then the resultant assembly is set in a heating furnace. In the heating furnace, the assembly is heated at a temperature (for instance 600.degree. C.) which is higher than the melting point of the brazing material applied to at least one of two members (which are to be connected to each other) and is lower than the melting point of the base material (the aluminum alloy which is the core material of each member to maintain its mechanical strength high enough). In those members, the brazing material on each member is molten, so as to be connected to the mating member. In the above-described members, the first header pipe 6a and the liquid tank 3 are both large in thermal capacity, and therefore the brazing of those members 6a and 3 are rather difficult. That is, the members 6a and 3 are increased in temperature slowly when compared with the other members; that is, the melting of the brazing material on at least one of the two members 6a and 3 takes time, so that the resultant brazing of the two members 6a and 3 is liable to be unsatisfactory. In addition, the time required for those members 6a and 3 to be connected to each other by brazing is unavoidably long; that is, the assembling work of the liquid tank and the condenser (including the brazing work) is low in work efficiency. Since the members 3 and 6a are cylindrical, the contact surface of them is linear, so that the brazing area is small, and the coupling force is not great enough. As was described above, in the case of the conventional structure, the brazing of the first header pipe 6a and the liquid tank 3 is not achieved satisfactorily, the assembling of them is low in work efficiency, and the coupling force of them is also inadequate. In the above-described case, the first header pipe 6a is connected to the liquid tank 3 by brazing; however, they may be connected to each other with metal members or the like. However, this method is rather troublesome. In order to increase the coupling force of the liquid tank 3 and the header pipe 6a, those members 3 and 6a may be so modified that they are flat in section, thereby to increase the coupling area of them. However, the method is undesirable, because the modification lowers the pressure withstanding characteristic.